Carbon–nitrogen bond

A carbon–nitrogen bond is a covalent bond between carbon and nitrogen and is one of the most abundant bonds in organic chemistry and biochemistry.^[1]

Nitrogen has five valence electrons and in simple amines it is trivalent, with the two remaining electrons forming a lone pair. Through that pair, nitrogen can form an additional bond to hydrogen making it tetravalent and with a positive charge in ammonium salts. Many nitrogen compounds can thus be potentially basic but its degree depends on the configuration: the nitrogen atom in amides is not basic due to delocalization of the lone pair into a double bond and in pyrrole the lone pair is part of an aromatic sextet.

Similar to carbon–carbon bonds, these bonds can form stable double bonds, as in imines; and triple bonds, such as nitriles. Bond lengths range from 147.9 pm for simple amines to 147.5 pm for C-N= compounds such as nitromethane to 135.2 pm for partial double bonds in pyridine to 115.8 pm for triple bonds as in nitriles.^[2]

A CN bond is strongly polarized towards nitrogen (the electronegativities of C and N are 2.55 and 3.04, respectively) and subsequently molecular dipole moments can be high: cyanamide 4.27 D, diazomethane 1.5 D, methyl azide 2.17, pyridine 2.19. For this reason many compounds containing CN bonds are water-soluble. N-philes are group of radical molecules which are specifically attracted to the C=N bonds.^[3]

Carbon-nitrogen bond can be analyzed by X-ray photoelectron spectroscopy (XPS). Depending on the bonding states the peak positions differ in N1s XPS spectra.^[4][5][6]

Nitrogen functional groups

Chemical class	Bond order	Formula	Structural Formula	Example	Avg. C–N bond length (Å)[7]
Amines	1	R3C-NH2		Methylamine	1.469 (neutral amine) 1.499 (ammonium salt)
Aziridines	1	CH2NHCH2		Mitomycin	1.472
Azides	1	R2C-N3		Phenyl azide	1.38–1.48[8] 1.47 (methyl azide)[9] 1.432 (phenyl azide)[10]
Anilines	1	Ph-NH2		Anisidine	1.355 (sp2 N) 1.395 (sp3 N) 1.465 (ammonium salt)
Pyrroles	1			Porphyrin	1.372
Amides	1.2	R-CO-NR2		Acetamide	1.325 (primary) 1.334 (secondary) 1.346 (tertiary)
Pyridines	1.5	pyr		Nicotinamide	1.337
Imines	2	R2C=NR		DBN	1.279 (C=N bond) 1.465 (C–N bond)
Nitriles	3	R-CN		Benzonitrile	1.136
Isonitriles	3	R-NC		TOSMIC	1.154[11]

See also

• Cyanide
• Other carbon bonds with group 15 elements: carbon–nitrogen bonds, carbon–phosphorus bonds
• Other carbon bonds with period 2 elements: carbon–lithium bonds, carbon–beryllium bonds, carbon–boron bonds, carbon–carbon bonds, carbon–nitrogen bonds, carbon–oxygen bonds, carbon–fluorine bonds
• Carbon–hydrogen bond